Comparative Analysis of SiO2 and FePO4 Crystal Structures

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Figure 1 Crystal Structure of SiO2 and FePO4 This paragraph will compare and discuss the crystal structure and chemistry between quartz (SiO2), iron phosphate (FePO4) and also looking into the α and β phase of FePO4. From the understanding of the given materials and crystal structure of both SiO2 and FePO4, both of the crystal are quartz-type crystal, the crystal arrangement are quite similar except for the difference in structural parameters tilt angle δ and bridging angle θ. This similarly carries on from the fact that both crystals had a α-β transition. However, from figure 2, the transition temperature for SiO2 and FePO4 are dramatically different, where one is at 846K while the other is 980K respectively. This is due to the tilt and bridging angle is lower than SiO2. Also from figure 2, we can show that both SiO2 and FePO4 thermal expansion in α phase are non-linear and control by angular variations and similarly no thermal expansion in β phase due to the lack …show more content…

The bond distance of Fe-O was found to be decreasing with each increase in temperature, as indicated in figure 3. This was observed to be similar to the Si-O bond distance in the SiO2. This is due to the increasing in disruption at high temperature arise from the excitation of energy levels and amplitude vibrations. Next, the α-β phase transition can be quantified using the tilt angle δ by modelling using this expression: δ2 = 2/¬3δ02 [1 + (1 – 3/4 (T – Tc/T0 – Tc)) 1/2 From figure 4 and formula, essentially explain the lack of thermal expansion activity during β phase is due to the fact that tilt angle δ has settled at zero which causes the removal of expansion components and discontinuity

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